I’ve managed to avoid working with Microsoft’s Active Directory for many years, which is actually somewhat of a skill. But recently a client, unhappy with the support and the direction their MS “specialist” was taking them, asked me to see what I could do with their network.

Long ago I advised them to steer clear of Active Directory if they could, because it would only tie them in to more and more expensive MS “necessities” over time. This is the position they found themselves in, years later, having to shell out more and more money to MS and their MS-oriented “consultant” just to keep things running – and not running well, either.

It was important to this company that they remain able to manage user identity and authentication from a central place, as well as authorities and permissions. So I thought it might be a good time to at last examine Samba-4 and its claims to support Active Directory.

The Samba-4 guys can claim anything they like related to Active Directory and I would be none the wiser. I knew nothing of AD. But that soon changed as I delved into Samba-4. I must point out that the things I say here are my own impressions and conclusions based upon next to no research – so I could be quite wrong in some places.

It turns out that Active Directory is an unholy marriage of DNS, Kerberos, LDAP and CIFS. Unholy only in that it tries to obscure the individual technologies. On the MS side of things, they like to include DHCP, but it isn’t necessary at all.

Maybe I shouldn’t say that it tries to obscure the individual technologies. Maybe I should say it tries to unite them in holy simplicity for the good user. Yes, that’s it.

The tricky key (and shackle) is DNS. I always wondered why Windows clients had to use the Active Directory server as their DNS server – it seemed so limiting (and error-prone). It turns out that Active Directory will “inject” funny yet specific DNS names into your domain that identify the AD server to clients. It’s not necessary to be designed that way of course, really – but it’s a good hook. Windows clients joining a “domain” expect these funny DNS entries, and it does no good just specifying the AD server to connect to, unless you have these DNS entries being injected there as well. (salutes and rifle fanfare, etc.)

As for Kerberos and LDAP – anyone who’s worked with them knows it can take some strenuous wrestling to get stuff seated and right for handling your user auth stuff. And in this I am actually impressed with Active Directory. MS has done a great job integrating these Free technologies into something standardized on a platform. Although there are many ways this can be accomplished, Microsoft’s dominance on client machines made a standardization possible. And I’m happy that the European courts saw fit to rule in a way that allowed these Free technologies to be free once again — and this is where Samba-4 comes in.

If you have worked with Samba in the past, you know how versatile it is for file serving, and how complicated it can get. I don’t think I’ve ever dealt with a longer man page with more options. Samba 4 is no different. However, in some ways, it’s much easier than Samba 3 if you’re using the standard Windows administration tools to administer the users and shares. From my understanding so far, you basically just put the shares you want into the smb.conf file with minimal definitions, and define the user authority stuff through the Windows tools connected as an Administrator to Samba 4. If you’re managing rights on share servers other than your Samba 4 DC, then you don’t even have to worry about defining them in the smb.conf file.

But of course you can if you want – there is a command line tool that gives you access to the same stuff that tweaks this marriage of Kerberos, LDAP and DNS – without the need of Windows at all.

Anyway, enough of these background thoughts. The Samba team has done a great job. A really great job. And I’m going to donate some dollars to them, because they do need pizza, even though they say they don’t.

So, being mostly a Debian guy, I decided to try this Samba-4 out in Debian Wheezy. The Wheezy repositories have an older version of Samba-4, of course. This is one of those rare instances where I will compile my own version of a package outside the normal Debian space, since Samba-4 is such a newer and only recently became stable, in the more unix-y sense of stability.

And it’s not that hard to compile and get Samba-4 running in Debian Wheezy. And it’s certainly worth the time if you want to replace an Active Directory Domain Controller with Samba-4 or to just play with it, to see what it’s all about. I took some notes while I was doing it, which I decided to share here, since other people have found my doing so helpful previously, on other systems.

Note: It looks like Debian Backports is updated with a newer version of Samba4 at last. This is a great way to go to avoid compiling and maintaining your own. I’ve tried it, and it works well. FYI

Do Your Debian

I used a KVM virtual machine to create a Debian Wheezy installation that would run Samba-4. I think it’s probably a good idea not to use a production server at first. If you use a VM, you can always just trivially put it into production later.

During the install, I chose the most minimal installation package option with the addition of an SSH server.

Of course, this will probably work just as well with other distributions if you get your library dependencies right. Ubuntu may work with no modification, but I’m not sure.

Kerberos is very finicky about time. You will need an ntp server to keep your clock well synchronized.

apt-get install ntp

Also, generally I like to assign my servers static IP’s. And it also seems like the AD stuff does not like changing IP addresses once it’s been set up. Seriously. It’s probably an ingredient in the unholy glue.

As for DNS, you can use Bind9 just fine with Samba 4 — but Samba 4 also has its own built-in DNS server that does that filthy injection. If you want to use Bind9 as your backend DNS server, you can, but you will need to allow the Samba 4 server to dynamically update the zone for your domain with Kerberos. There are howto’s on that. I chose to just let Samba 4 use its own built-in DNS server. Because I’m lazy. And I’m just playing for now. And I don’t like a “domain controller” being able to update my real DNS zone file.

This leads to an interesting, and by that I mean boring and unnecessary, discussion of how you should name your Active Directory “domain”. There are a few schools of thought on it, and even Microsoft has changed their tune over time on the subject. I have chosen to name my Samba 4 “domain” as a “subdomain” of my root domain – that way the Active Directory stuff doesn’t have to be authoritative for my whole domain, and I don’t have to make up a fake domain either.

And leave it to Microsoft to terribly confuse everyone by “making it easy”. By domain they do not mean a DNS domain. It’s a hybrid abomination of DNS and what is known in Kerberos as a “realm”.

So yes, well, I made Samba 4 be the DNS server, but it will also do sensible lookups to the real DNS information from my proper DNS server when it doesn’t know a name. That’s why I named it as a DNS “subdomain” (host) rather than the whole domain. For resolution:

edit /etc/resolv.conf

Now, in Ubuntu you’re going to have to do some special editing of configs to keep Network-Manager from overwriting your resolv.conf file after you make these changes.

The first should be your Samba 4 installation IP. The second should be your real DNS server.

Probably quick & dirtiest to reboot after all this, if you like that sort of thing. BTW – make sure your /etc/hostname matches your DNS hostname. I don’t know if it’s necessary, but how can you stand it otherwise??

Debian Requirements to Compile Samba 4

I should mention, if you plan on having your Samba 4 server also be a filesharing server, and for the Active Directory stuff to manage the users and permissions for you, you need to make sure that whatever filesystem you’re going to be serving out is supporting ACL’s and extended attributes. In Debian this is a normal part of their ext4 mounts, and I think their ext3 ones as well. So you’re set!

But still, might be good to put it in, in your /etc/fstab, just as a reminder. Do, of course, use your own partition’s UUID. And whatever mountpoint you want to share.

Many docs also want you to specify barrier=1 as a mount option, to make sure stuff doesn’t get corrupt in a power failure. This is enabled by default in ext4, but you may want to in ext3. And if you’re using LVM volumes, this is passed through and respected now. Ah, the wonders of the modern world.

Now, what you really want to know: which Debian packages do I need to install when compiling Samba 4? Well, how about these?

If you don’t have other Kerberos servers, well, I just used this server as my kerberos ones, and it works just fine. The initial realm, where it defaults to your domain name in upper-case — I made that the FQDN in upper-case as well. Apparently the realm likes to be upper-case.

Maybe you’ll want to reboot again, after the acl stuff. Maybe not. Maybe you didn’t reboot a few minutes ago, so it will only be this one reboot. Or none. I don’t care.

Compile Samba 4

The version of Samba I grabbed was their latest at the time, listed below. They may have a newer version when you read this, so always check the Samba site for the version you want.

I like compiling in /usr/src — and I’m letting Samba 4 install to its default location, which I know is a horrific violation of Debian policy. But I’m naughty.

After that completes successfully the first try and love descends upon all humanity, you might want to put the install directory into your PATH environment variable so you can avoid over-stressing your poor little phalanges. Put this in your .bashrc

export PATH=/usr/local/samba/bin:/usr/local/samba/sbin:$PATH

If you’re feeling particularly cavalier, trusting in the goodness of strangers that is. And source it! (or log out/in, open a new terminal, whatever)

I also symlinked my /usr/local/samba/etc to /etc/samba to make it less typing to edit configs:

ln -s /usr/local/samba/etc /etc/samba

Then you’ll want to make the Samba 4 stuff work. Right? First thing is to provision the so-called domain. I’m leaving it open to do some Un*x-side integration later here – that’s why the “rfc” switch.

samba-tool domain provision --use-rfc2307 --interactive

It will ask you some questions, and here’s where we get into the “domain” naming philosophy again. Just make it the same as your DNS decision above. In my example, the Realm I chose was SAMBA4.MYDOMAIN.COM

Do do the upper-case! Why? I don’t know!

And for the “Domain” I chose “MYDOMAIN” (without the .COM). It’s pretty much like your workgroup setting, is all I can figure.

If you do it this way, then all machines joining your Active Directory “domain” will get the right DNS information for your DNS zone — because the AD server will only consider itself authoritative for SAMBA4.MYDOMAIN.COM and “higher”, but not for all of MYDOMAIN.COM itself — and it will forward those DNS requests on to your proper DNS server when it doesn’t know about them.

So be sure to set your DNS forwarder here to your real DNS server.

Cold, Cruel Kerberos

I’ve never know it to be so easy. I’m leaping with joy inside. Or maybe that’s lasagna.

That’s about it! You can now fully administer it just like an Active Directory domain controller from Windows, using their remote server administration tools. Crazy, I know! That link is for Windows 8.1 download, BTW.

The thing is, when you join a Windows machine into the “domain”, you have to make sure that you’re using your Samba 4 server as the DNS server for that machine, just like you would have to do with Microsoft’s Active Directory domain controllers. They need the filthy DNS injection.

Home Directories for Windows Users

If you want to have your Samba 4 server serve out home directories to your users, you accomplish that pretty easy. It just requires a “[home]” section in your smb.conf file.

That’s not a “[homes]” section like in Samba 3 by the way — just a singular “[home]”. It’s special. Apparently.

That section only requires a path and a not-read-only:

[home]
path = /home/
read only = no

You don’t really need local accounts for your users. Samba 4 will create crazy high-numbered fictional users and groups to service your Windows throngs. Just make sure that mountpoint has the acl and xattr flags.

Oh, and your administrator account will need the “SeDiskOperatorPrivilege” I think:

This will make it so that, if you use the Windows remote administration tools in Windows, you can create users that can have a drive automatically mapped to their Windows machine when they log in, and Samba 4 will create their home directory automatically.

It should also be noted that the default setup seems to allow normal workgroup functioning to continue working as well. So even if you have Windows machines that aren’t the insanely more expensive “Pro” version of Windows, you can still map to the shares like you could to a workgroup.

But then again, that begs the question, why then bother with an Active Directory Domain Controller at all? Unless you want to spend a lot more money per seat on Windows.

Final Comments

I am impressed with Microsoft’s ability to impose a standardized way of implementing LDAP in conjunction with Kerberos. I am less impressed with their shameless violations of DNS to rope this in.

I haven’t tried it yet, but apparently you can pretty easily have your Linux boxes authenticate against Samba 4 as well. I think I may not be doing that. Well, maybe I will.

It is really nice and compelling that it’s all tied together. And it’s not so bad since Samba 4’s been able to bring it into the light. I’m undecided. It seems to work well.

Anyway, I hope this helped someone. I was very daunted by the whole Active Directory integration mess at first. But these Samba guys really have done a great job. I’ll be showing them some love. Of the monetary type! Well, I suppose unless…